In numerous installations, a water pump and the electric motor which operates the pump are submerged within the body of water from which water is pumped. In some water pump installations, a water pump and an electric driving motor may be located a considerable distance from the electric control unit which supplies electrical energy to the electric motor. In each water pump installation, there is a possibility that the supply of water at the pump may cease or a coupling between the driving electric motor and the water pump may break, or for some other reason the electric motor operates without pumping operation of the water pump. If the supply of water to the water pump ceases, the pump may be severely damaged if it is operated. If the coupling between the electric motor breaks or for some other reason the pump is operated without pumping action, a signal should be provided in regard to such a condition, and/or the motor should be deenergized. However, numerous electric motors which operate water pumps have no protection against a condition in which the motor is operating while the pump is not pumping water. Therefore, such installations endanger the electric motor.
Also, most installations which include means for protection of a water pump employ a motor control unit which is attached to support structure and also employ a pump protective unit which is separately attached to the support structure adjacent the motor control unit. The pump protective unit is electrically connected to the motor control unit. Thus, there are at least two units mounted upon support structure. Electric wires from a source of electrical energy are connected to the protective unit. Then electric wires are extended from the pump protective unit to the motor control unit, and the wires are connected to the pump protective unit and to the motor control unit. Then, electric wires are extended from the motor control unit to the electric motor, and the wires are connected to the motor control unit and to the electric motor. Therefore, a plurality of units are mounted upon support structure and numerous electric wires are attached to the units and extend to and from the units and to the electric motor.
U.S. Patents which show protective electrical circuitry are U.S. Pat. Nos. 2,953,722, 3,417,290, 3,519,910, 3,600,657, 3,727,103, 3,931,559, 3,953,777, 4,034,269, 4,091,433, 4,117,408, 4,286,925, 4,290,007, 4,420,787, 4,642,478, 4,703,387.
However, none of these patents shows structure in which a protective unit, as a module, is readily attachable to a motor control unit to form a combined assembly, without the mounting of an additional unit upon support structure, and without the necessity of additional conventional wiring.
It is an object of this invention to provide means and a method by which an electric motor control unit which is mounted upon support structure can be readily and easily equipped with pump protection means without the necessity of mounting a separate motor protective unit upon the support structure and without the necessity of attaching conventional electric wires between the motor protective unit and the motor control unit.
Another object of this invention is to provide a pump protective unit which constitutes a module which is readily attachable to an electric motor control unit.
Another object of this invention is to provide a plug-in type electric motor protective unit which is adapted to plug-in to an electric motor control unit which is mounted upon support structure whereby the two units become a single assembly, without the necessity for conventional mounting and without the necessity of conventional electric wires between the units.
Other objects and advantages of this invention reside in the construction of parts, the combination thereof, the method of construction and assembly and the mode of use, as will become more apparent from the following description.